<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="app">
  <span v-if="isUser">
  <label for="username">用户账号</label>
  <input type="text" id = "username">
  </span>
  <span v-else>
  <label for="useremail">用户邮箱</label>
  <input type="text" id="useremail">
  </span>
  <button @click="isUser = !isUser">切换类型</button>
</div>

<script src="../js/vue.js"></script>
<script>
    const  app = new Vue({
      el:'#app',
      data:{
        message: '卢本伟牛逼！',
        isUser: true
      },
      methods: {

    }
    })
</script>
</body>
</html>